sig
type t = string
val equal : t -> t -> bool
val hash : t -> int
val compare : t -> t -> int
val prefix : string -> string -> bool
val fold_left : ('a -> char -> 'a) -> 'a -> string -> 'a
val fold_right : (char -> 'a -> 'a) -> string -> 'a -> 'a
val explode : string -> char list
val implode : char list -> string
end